We present the low-resolution transmission spectra of the puffy hot Jupiter HAT-P-65b (0.53 MJup, 1.89 RJup, Teq = 1930 K), based on two transits observed using the OSIRIS spectrograph on the 10.4 m Gran Telescopio CANARIAS. The transmission spectra of the two nights are consistent, covering the wavelength range 517–938 nm and consisting of mostly 5 nm spectral bins. We perform equilibrium-chemistry spectral retrieval analyses on the jointly fitted transmission spectrum and obtain an equilibrium temperature of 1645 (-244+255) K and a cloud coverage of 36 (-17+23) %, revealing a relatively

In a star like the Sun, surface magnetic activity results from the interaction between rotation, convection, and magnetic field. One of the key parameters to study the magnetic activity of stars is the Rossby number, which is the ratio between the surface rotation period of the star and the convective turnover time. The convective turnover time measures the time that takes a bubble of plasma to go from the base of the convective zone in a star like the Sun to the surface, similarly to a bubble reaching the surface in a pan with boiling water heated by the bottom. While the surface rotation

The solar coronal heating problem originated almost 80 years ago and remains unsolved. A plausible explanation lies in mechanisms based on magnetic wave energy dissipation. Currently, several linear and nonlinear wave damping models have been proposed. The advent of space instrumentation has led to the creation of catalogues containing the properties of a large number of loop oscillation events. When the damping ratio of the oscillations is plotted against their oscillation amplitude, the data are scattered forming a cloud with a triangular shape. Larger amplitudes correspond in general to